As a DM, this is the norm. With the exceptions of PVG/PEK/SIN (routes where it's routine to have 25+ Diamonds on a flight), it's a bad and weird flight as a DM if the head person in your section isn't paying attention to you. This is in addition to the ISM and often SP greeting. (hence, reports about OWEs receiving "the" greeting here are usually off the mark, because as a DM there are frequently multiple greetings and someone looking after you).

This is more pronounced in Y and it's crew dependent - some crew really bend over backwards for DMs. And the good ones spoil you, so when you don't get the extra attention you notice it.

Hands down one of the more valuable aspects of Diamond to me was sitting in economy class, and having the section head (usually an FP) pay you a great deal of attention, plus alert all the BCs to do the same. Forget the ISM or even the SP, when the FP in your section and BCs are all helping you out, that's where the value is. I don't fly economy much anymore so I'm not as familiar these days, but that always stood out to me. When you had a great FP overseeing your section with alert BCs, service was spectacular. The ISM or SP greeting was all style but the FP/BC was substance.

Tied into another thread going on, one "problem" with having GO/DM status and flying almost exclusively J and F is you don't really notice the difference. The difference in treatment in Y is significantly greater than in J or F.